Ion generator having a metal plate that produces ionizing photoelectrons upon exposure to ultra-violet light



Aug 8, 1957 G. s. DlcKlNsoN ETAL 3,335,272

ION GENERATOR HAVING A METAL PLATE THAT PRODUCES IONIZING PHOTOELECTRONS UPON EXPOSURE TO ULTRA-VIOLET LIGHT Filed June 7 1961 2 Sheets-Sheet l Aug- 8, 1967 s. DlcKlNsoN ETAL 3,335,272

ION GENERATOR HAVING A METAL PLATE THAT PRODUCES IONIZING PHOTOELECTRONS UPON EXPOSURE TO ULTRA-VIOLET LIGHT Filed June '7, 1961 2 Sheets-Sheet 2 photo emissive type negative ion in the number of electrons United States Patent Oli ice 3,335,272 ION GENERATOR HAVING A METAL PLATE THAT PRODUCES IONIZING PHOTOELEC- TRONS UPON EXPOSURE. TO ULTRA-VIO- LET LIGHT George S. Dickinson, Fairfield, and William A. Omohundro, Westport, Conn., assignors to General Electric Company, a corporation of New York Filed June 7, 1961, Ser. No. 115,349 2 Claims. (Cl. Z50-43) The present invention relates to an ion generator, and more particularly to a device for generating only negative ions and for discharging these ions into atmospheric air within an enclosed area such as a room.

Various devices have been used or proposed for discharging negative ions into a room. Some of these devices produce both negative and positive ions by thermonic emission, radioactivity and by the action of electric fields. With these systems both positive and negative ions are generated and some means is usually provided for neutralizing the positive ions so that only the negative ions are discharged into the room. It is also known that negative ions may be generated by photo emission. In the operation of such a system a body is bombarded with photons which are irradiated from a suitable source, such as ultra-violet light, to causernegative electricity or electrons to leave the body and follow electrostatic lines of force. The electrons emitted from the body attach themselves to molecules which are present in the air and the molecules having picked up a free electron become negative ions. 'I'his invention is concerned with such a generator.

It is a primary object of this invention to provide an improved photo emissive itype ion generator having a high electron emission and ion generation rate.

Another object of the invention is to provide an improved ion generator for discharging the negative ions before they become neutralized within the ion generator by coming into contact with neutral or positively charged bodies within the ion generator.

It is a further object of this invention to provide an improved ion generating device having an electron emitting plate which will continue to eiectively emit electrons although grease may be adsorbed by the emitting plate.

Briefly stated, in accordance with one aspect of the invention, an object is arranged for bombardment by a source of irradiation for emitting electrons to form ions, and the electron emitting plate is impressed with a negative voltage to repell the negative charges which are formed within the ion generator. The voltage is so selected that the ions will travel very slowly from the object to the source of irradiation along the electrostatic lines of force between the electron emitting object and the source of irradiation. While the negative ions are slowly being repelled from the object toward the source, they are also being acted -upon by an airstream of predetermined velocity which carries the generated ions through the air gap between the electron emitting object and the source and discharges them from the ion generator before they become neutralized. By this arrangement a relatively great number of negative ions may be generated and swept into a room before the ions or the electrons emitted from the plate fall back to the electron emitting object, reach the source of irradition, or become neutralized or adsorbed in some other manner. In addition, with such an arrangement, continued operation of the ion generator does not result in an appreciable decrease emitted from the object or in the number of ions generated although grease may be adsorbed on the emitting object.

3,335,272 Patented Aug. 8, 1967 Further objects and advantages of the invention as well as other moditications thereof will become apparent as the description proceeds. This invention will be better understood by reference to the accompanying drawings in which:

FIG. l is a perspective view of an ion generating un-it embodying the invention; and

FIG. 2 is a circuit diagram for the device illustrated in FIG. l.

Referring now to FIG. 1 of the drawings, there 1s illustrated an ion generator comprising a housing or casing 1 which suitably encloses the operative parts of the ion generator. The casing 1 preferably is made of sheet metal and includes a top wall 2, shown broken away for purposes of illustration, a bottom wall 3, side Walls 4, rear wall 5 and front Wall 6. The front wall 6 is formed with an ionized air discharge opening 7 which may be provided with a grille 8. A suitable air inlet opening 9 is provided in the bottom wall 3 of the ion generator, and a fan 10 is arranged for forcing air through the ion generator in a manner to be more particularly described hereinafter.

In the embodiment illustrated, a tubular ultra-violet ray lamp 11 is provided as the source of irradiation and the lamp is suitably mounted at the rear of the casing between vertically disposed electrode supporting brackets 12. An elongated metal plate 13 is provided for emitting electrons when it is bombarded by photons from the source of irradiation 11. The plate 13 is preferably formed of tin or other suitable metal which will emit electrons. As shown, the plate partially surrounds the source of irradiation 11 to provide an air gap 14 between the plate and the ultra-Violet lamp. l

Referring now to the circuit diagram of FIG. 2, y1t is evident that the ultra-violet lamp 11 may be suitably connected to a standard volt 60 cycle alternating current source by a conventional plug connector 1S. A starter 16 and a ballast 16 are also connected in the circuit in a conventional manner for properly energizing the ultra-violet lamp 11. As shown, a fan motor 17 is connected in parallel with the ultra-violet lamp and a switch 18 is provided for simultaneously energizing the fan motor 17 and the ultra-violet lamp 11.

With this arrangement photons from lamp 11 may bombard plate 13 to cause electrons to leave the plate and follow electrostatic lines of force in the air gap 14 between the plate 13 and the lamp 11. It is believed that these electrons attach themselves to gas molecules which are present yin the air gap 14 to form ions. These ions attract water molecules and it appears that approximately ten molecules of water may be united with one of these ions to form an airborne ionized particle.

A unique arrangement is provided for substantially increasing the number of electrons emitted from plate 13 While the plate is being bombarded by photons from the ultra-violet lamp. Thus, with an increase in the number of free electrons there is a corresponding increase in the number of ions which may be formed in the air gap 14. These improved results are achieved by connecting the plate 13 to the line side of the ultra-violet lamp through a diode 19 oriented with its cathode connected to the line and its anode to the plate 13. With this construction, stray capacitance exists between the plate 13 and its surroundings as illustrated by the dotted line phantom circuit shown in FIG. 2. In the embodiment illustrated, this stray capacitance amounts to approximately .O02 microfarad and causes an alternating current voltage to be induced on the plate. This alternating current voltage is rectified by the diode 19. By this arrangement, the negative polarization of the plate dispels an electron space charge at the plate to thereby greatly 'increase the number of ions generated by insuring that electron enough energy to pass through the layer of l contaminant.

While it is preferable to employ silicone diodes for effectively polarizing the plate 13, transistors used as diodes have also been found to be suitable. With the use of a PNP transistor, the N lead woud be connected tothe line, while one of the P leads would be connected to the emitting plate. It will also be understood that the plate may be eectively polarized with a battery applied voltage, or the plate may be connected to ground through a suitable transistor or diode.

A line current limiting resistor 20 may be located in series with the diode between the diode and the line to eliminate shock hazard, and in the embodiment illustrated the value of the resistor and the diode and the other parameters of this circuit are so selected so that the plate -is made negative by approximately 40 volts with respect to the lamp 11.

It is desired to provide a definite relationship between the plate voltage, the distance from the ultra-violet lamp to the plate, the air velocity through the air gap, and the length of the air gap from the point at which air enters the space between the lamp and the plate to the point at which the air is discharged from the air gap. In the embodiment shown in FIG. 1, two different air streams are caused to ow through two air gaps in which ions may be formed. Airis drawn in through opening 9 by fan 10 and is directed by the baffle walls 21 to the central portion of the ultra-violet lamp 11. As it reaches the lamp, the air is split into two streams. One stream ows to the left through a left ion air gap between the plate 13 and the ultra-violet tube 11, it is discharged from the air gap, ows along the left side wall 4, and is directed by the baille walls 21 out of the casing through opening 8. 'I'he second air stream flows to the right through a right -air gap between the ultraviolet lamp 11 and the plate 13, it is 4discharged from this air gap and flows along the right wall of the casing and out through opening 8. The velocity of the air through the air gap between the plate and the ultra-violet lamp is selected so that an ion which is formed at the central portion of the plate 13 at the air intake portion of either one of the air gaps will be carried through one of the air gaps before it can be repelled to the lamp by the voltage applied to plate 13. In this manner, the ionized molecule remains an ion and does not become neutralized, or adsorbed. For example, in the embodiment illustrated, the average distance from the target to the lamp is approximately .375, the length of the left air gap is l, while the length of the right air gap is 7, and the plate 13 is made negative by approximately 4Q volts with respect to the lamp. With reference to the air gaps, the air velocity through the gaps is more than 500 feet-per-minute. y'

While there has been shown and described a specific embodiment of the invention, it is not desired that the invention be limited to the particular form shown and described, and it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention. For example, the emitting plate may be formed as a cylinder which surrounds the ultra-violet lamp, and air may be forced in one end of the annular gap between the plate and the tube and out through the other end of the air gap without departing from the spirit of the invention.

What we claim is:

1. An ion generator comprising: a source of alternating electric current, an ultra-violet lamp for irradiating photons connected to said `source of alternating electric current, a plate located adjacent to said ultra-violet lamp whereby the photons irradiated from said lamp may cause electrons to be emitted from said plate, said lamp and said plate being arranged to form .an air gap separating the plate from the lamp, means for introducing molecules which are capable of being ionized into said air gap so that the molecules may pick up the electrons emitted by said plate and form negative ions, a diode connected to said plate and to said alternating electric current source for impressing a negative voltage on said plate to dispel electron space charge and to repell the negative ions from said plate.

2. An ion generator comprising: a source of irradiation for irradiating photons, a plate formed of tin located adjacent to said source of irradiation whereby the photons irradiated from said source may cause electrons to be emitted from said tin plate, said source of irradiation and said plate being arranged to form an air gap separating the plate from said source, means for introducing molecules which are capable of being ionized into said air gap so that the molecules may pick up the electrons emitted by said tin plate and form negative ions, silicone diode means for impressing a negative voltage on said plate to dispel electron space charge and to repell said negative ions from said plate, and means for causing an air stream to ow in said air gap for discharging said ions from said air gap before they become neutralized.

References Cited UNITED STATES PATENTS 1,965,187 7/1934 Hartman Z50-43 2,628,083 2/1953 Rense 26.1--137 2,855,641 10/1958 Stein 250--43 FOREIGN PATENTS 420,360 1l/ 1934 `Great Britain.

RALPH G. NILSON, Primary Examiner. W- Ff LINDQUIST, Assistant Examiner, 

1. AN ION GENERATOR COMPRISING: A SOURCE OF ALTERNATING ELECTRIC CURRENT, AN ULTRA-VIOLET LAMP FOR IRRADIATING PHOTONS CONNECTED TO SAID SOURCE OF ALTERNATING ELECTRIC CURRENT, A PLATE LOCATED ADJACENT TO SAID ULTRA-VOILET LAMP WHEREBY THE PHOTONS IRRADIATED FROM SAID LAMP MAY CAUSE ELECTRONS TO BE EMITTED FROM SAID PLATE, SAID LAMP AND SAID PLATE BEING ARRANGED TO FORM AN AIR GAP SEPARATING THE PLATE FROM THE LAMP, MEANS FOR INTRODUCING MOLECULES WHICH ARE CAPABLE OF BEING IONIZED INTO SAID AIR GAP SO THAT THE MOLECULES MAY PICK UP THE ELECTRONS EMITTED BY SAID PLATE AND FORM NEGATIVE IONS, A DIODE CONNECTED TO SAID PLATE AND TO SAID ALTERNATING ELECTRIC CURRENT SOURCE FOR IMPRESSING A NEGATIVE VOLTAGE ON SAID PLATE TO DISPEL ELECTRON SPACE CHARGE AND REPEL THE NEGATIVE IONS FROM SAID PLATE. 